Table 1.

The advantages and limitations of different types of stem cells in SCI therapy.

Type of Stem Cells	Benefits	Restrictions	Ref.
Embryonic stem cells	Remarkable proliferative capacity In vitro and in vivo pluripotency Ability to differentiate into cells of ectodermal origin Promotion of the sprouting function Providing a scalable, tractable, and accessible high-throughput platform for decoding mammalian embryogenesis at a high level of resolution İnducing myelination Good source of differentiation to oligodendrocytes and motoneurons	Ethical controversies Partial recovery of forelimb motor after being transplanted into both chronic and acute cervical spinal cord injury rat models Probability of tumor formation	[35,36,47]
Induced pluripotent stem cells	Prevention of ethical considerations and immunological rejection via use of patient-specific iPSCs Inhibition of neuronal apoptosis Promotion of myelin production by oligodendrocytes Modulation of immunopathological events	Inhibition of restorative effects of the transplantation via GAS5 silencing gene Several risks, such as uncontrolled expression of integrated transgenes, insertional mutagenesis, tumor formation, and silencing or downregulation of transgenes Aberrant reprogramming Presence of transgenes	[39,40,47]
Mesenchymal stem cells	Easy isolation (from different sources) Good preservation Reduction in ethical concern Reduced risk of tumors development High regenerative potential after freezing Rapid proliferation Obtaining high multilineage differentiation Low immunoreactivity “Homing” capability Control of the effects of secondary injury (after SCI) Establishment of higher recovery of nerve functions	Low survival rate Lack of enough evidence on differentiating MScs to neuronal cells Differentiation of transplanted cells into other types of cells, such as osteoblasts, which limits their therapeutic effects Unsatisfactory translation from small animal experimental models (mice and rats) into human clinical practice Usually have paracrine activity instead of cellular replacement mechanisms	[48]
Neural stem cells	Promotion of remyelination of axons High self-renewal capability in in vitro culturing More preferable than hESCs in clinical applications Less potential of tumor formation	Glial scar formation Limited differentiating potential in clinical trial after several passages Their cell survival and integration highly dependent on their source of transplantation and isolation methods Need purification Moderate cell survival İnefficient tracking systems Lack of neurotrophic factors	[49]